High speed optical communications systems are generally known. Such systems typically include a transmitter optical subassembly (TOSA) and a receiver optical subassembly (ROSA) connected via an optical fiber.
The TOSA may generally include one or more laser diodes. In some devices, an array of vertical cavity surface emitting lasers (VCSELs) are used to generate optical signals that are coupled through an optical fiber ribbon that includes an equal number of fibers. A corresponding array of photodetectors within the ROSA are used to detect a respective optical signal within each of the optical fibers of the fiber ribbon.
The TOSA and ROSA are often operated in the GHz range. As with any device operated at such a high frequency, optical transceivers generate significant electromagnetic interference (EMI).
EMI generated by electro-optical converters generally propagates in all directions. In order to minimize such radiation and in order to meet FCC requirements, manufacturers usually enclose the ROSA and TOSA in an electrically conductive housing. The electrically conductive housing absorbs and reduces EMI.
However, the electrically conductive housing must be provided with openings for electrical and optical connections (e.g., an electrical cable, a “ribbon” of multiple parallel optical fibers, etc.). Whenever the external housing is penetrated by an electrical or optical connection, the potential exists for EMI leakage. Moreover, when a fiber ribbon is used, the EMI emitted may increase in direct proportion to the number of fibers in the fiber ribbon due to the larger hole. Because of the importance of optical communications, a need exists for better methods of reducing the leakage of EMI where a ribbon of optical fibers enter a housing.